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Transport processes in hydrogels
Sárová, Michaela ; Kalina, Michal (referee) ; Klučáková, Martina (advisor)
This master's thesis is focused on study of transport processes in hydrogels based on humic acids. For this purpose is used methods unsteady diffusion in cuvettes, which was studied the transport of organic dyes, specifically methylene blue and rhodamine 6G, in agarose hydrogel without the addition and with the addition of individual standards humic acids (Leonardite, Elliott Soil, Suwannee River II and Pahokee Peat). This method is based on spectrophotometric monitoring of concentration changes of dyes depending on space of the cuvette and on time. The aim of this thesis was to investigate the effects of interactions between diffusing dye and the particular type of gel to the resultant effective diffusion coefficient of dye. The experiments indicate that the presence of humic acid in the hydrogel greatly affects the transport of selected dyes.
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Inverse FCS in colloidal systems research
Richterová, Veronika ; Venerová, Tereza (referee) ; Mravec, Filip (advisor)
This diploma thesis is focused on the study of inverse fluorescence correlation spectroscopy, especially with the regard for the usage of different fluorescent probes and different sized analysed particles. At first, the proper concentration of fluorescent probes was determined. In this concentration is the probe considered as a medium surrounding the analysed particles. Based on this concentration, which was determined as 400 M, several sets of samples were prepared. This samples contained different concentration of polystyrene particles of 100 and 500 nm diameter and multilamellar liposomes. Then, the FCS curves of samples with different fluorescent probes were measured. Fluorescein, rhodamine 6G and Atto 488 were used as fluorescent probes. As a result from experiments, it was found, that particles with 100 nm diameter cannot be analysed with none of the fluorescent probes. Inverse FCS method can be applied to systems, that contains particles with 500 nm diameter and fluorescein. Systems with rhodamine 6G have the same behaviour as typical FCS measurement. It is caused by dimerization of this probe and it cannot be used for 500 nm particles. Liposome samples can be established with iFCS method, but the results are biased by random distribution of liposomes size.
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Transport properties of humic gels
Sárová, Michaela ; Pospíšilová, Ľubica (referee) ; Klučáková, Martina (advisor)
This bachelor’s thesis is focused on study of transport properties of humic gels. For research of these properties was used diffusion method of organic dyes in diffusion cells which is based on spectrophotometric monitoring of concentration changes depending on time. Dyes used in the experiment were specifically methylene blue and rhodamine 6G and diffusion experiments were performed on an agarose hydrogel without the addition of humic acid, with the addition of unmethylated humic acid and then with the addition of methylated humic acid. The aim of this thesis was to investigate the effects of interactions between diffusing dye and the particular type of gel to the resultant effective diffusion coefficient of dye. It has been found that the presence of humic acid in agarose hydrogel greatly influences the transport of dyes.
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Effect of chemical modification of humic acids on their interactions with organic ions
Fryšová, Eva ; Weidlich, Tomáš (referee) ; Sedláček, Petr (advisor)
This master thesis deals with the interaction of humic acids with organic ions and effect of chemical modification of humic acids on this interaction. Rhodamine 6G was used as a model organic ion. The interaction were studied by fluorescence quenching, dialysis in diffusion cells and differential UV-VIS spectroscopy. Results showed that the bond between the reactants was not primarily dependent on carboxylic functional groups of humic acids. Fluorescence experiments indicated static quenching mechanism and differential UV-VIS spectroscopy demonstrated the existence of - interactions.
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Study of barrier and transport properties of polyelectrolytes using diffusion techniques in hydrogels
Valentová, Kristýna ; Kalina, Michal (referee) ; Smilek, Jiří (advisor)
This diploma thesis was focused on study of barrier and transport properties of selected polyelectrolytes in hydrogel matrices by using diffusion techniques. The study of these properties was performed in horizontal diffusion cells where is observed the change in diffusion probe concentration over time. Diffusion experiments were performed on an agarose hydrogel with the addition of alginate, hyaluronic acid, polystyrene sulfonate, humic acids and as a model probe rhodamine 6G was used. Important parts of this thesis are also the methods which characterize the substances and hydrogel matrices such as rheology and potentiometric titration. The main aim of this diploma thesis was to investigate the effect of interactions between passing model dye (rhodamine 6G) and the appropriate gel (agarose + polyelectrolyte) on the fundamental diffusion parameters (effective diffusion coefficient, lag time, etc.).
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Study of optical properties of organic materials for nonlinear optical applications
Hrbková, Silvie ; Hrabal, Michal (referee) ; Vala, Martin (advisor)
This work deals with a development of a method for determination of two-photon parametres and its application. The theoretical part includes a description of two-photon absorption processes, most frequently used methods to determine two-photon cross sections and a summary of molecules researched to date in the field. The molecules studied in this work are Rhodamin B and Rhodamin 6G in ethanol, which are applied as standards for the implementation of the method. After that, Diketopyrrolopyrroles U24, U37, U49 and U50 dissolved in DMSO, toluene, acetone and chloroform, are researched. Basic optical characteristics - absoption and emission spectra were experimentally acquired for all the materials. Two-photon characteristics were obtained using a picosecond laser and a Two-Photon Excited Fluorescence (TPEF) method. TPA cross-sections and TPA spectra of Rhodamin B and Rhodamin 6G were measured and discussed. Subsequently, this work focuses on absorption and emission solvatation processes of the selected Diketopyrrolopyrroles. These processes indicate their two-photon efficiency. Finally, TPA spectra of the substances are discussed. Contribution of this work is a developed method for measuring the two-photon characteristics suitable for further use. The outcomes achived, enable extensive research of the Diketopyrrolopyrrols characteristics with the use of the measured standards of the Rhodamin B and Rhodamin 6G.
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Time-resolved fluorescence study of liquid and condensed systems based on biopolymer-surfactant interactions.
Černá, Ladislava ; Žitňan, Michal (referee) ; Mravec, Filip (advisor)
This thesis studies properties of hydrogel, which arises on the basis of electrostatic and hydrophobic interactions between hyaluronan chain and micelles of cationic surfactant. A native sodium hyaluronan at molecular weight 750–1 000 kDa and a cationic surfactant CTAB (cetyltrimethylammonium bromide) were used. This hydrogel was assessed as a material for drug delivery systems. The hydrogels were made by mixing 200mM CTAB with 0.5% hyaluronan, both dissolved in 0.15M aqueous solution of NaCl simulating physiological solution. Methods used in this study were steady-state and time-resolved fluorescence spectroscopy, more accurately time-resolved emission spectra (TRES) and deconvolution of steady-state emission spectra of a whole sample by means of parameters gained from fluorescence intensity decays at a set of wavelenghts. Selected systems were investigated by three fluorescent probes, prodan, laurdan and rhodamine 6G. The first two mentioned probes were in hydrogel localized only within micelles in three different microenvironments. Rhodamine 6G pointed out that in hydrogel the aqueous environment is significantly restricted in comparison to purely micellar solution. In addition, rhodamine informed about less available micelle surfaces, caused by hyaluronan chains occupation. There were no interactions between the probes and hyaluronan chains. Freshly made hydrogels showed almost the same results as after a week of maturation under its supernatant.
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Anisotropy and time-resolved anisotropy techniques in colloidal systems research
Holínková, Petra ; Táborský,, Petr (referee) ; Mravec, Filip (advisor)
In this diploma thesis were investigated in terms of microviscosity liquid and condensed systems composed of hyaluronan (Hya) and cationic surfactant cetyltrimethylammonium bromide (CTAB). The excitation and emission spectra, lifetime, steady-state fluorescence anisotropy and time-resolved fluorescence anisotropy of the samples were measured. First, was studied the formation of hydrophobic domains in the system Hya-CTAB at concentration of CTAB lower than its critical micelle concentration in an aqueous solution and 0.15M NaCl. It was found that in an aqueous solution small hydrophobic domains linked to chains Hya are formed. Then an increasing concentration of CTAB leads to phase separation and formation of gel. Due to the addition of NaCl then leads to the reorganization of this system and probably the formation of free micelles in the solution. Were also studied condensed phase of system Hya-CTAB-NaCl at high concentrations of surfactant during fourteen days of ageing. It was found that the microviscosity of hydrophobic domains is constant, but the microviscosity of hydrophilic parts gradually decreases.
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Diffusion properties of oppositely charged organic molecules in solutions of hydrophilic polyelectrolyte
Rýcová, Eva ; Márová, Ivana (referee) ; Mravec, Filip (advisor)
This work is focused on physical interactions of negatively charged polymers with small ionogenic fluorescent molecules. Trying to verify the presence of these interactions using fluorescence correlation spectroscopy (FCS) and provides a comprehensive view of the problem. The aim of this work is to observe the effect of concentration on the diffusion properties. P/D ratio, where P represents number of polymer binding sites and D number of dye binding sites, was chosen for this issue. Hyaluronate, sodium chondroitin sulfate and sodium polystyrene sulfonace were used as polymers and Acridine Orange, and Rhodamine 6G were chosen as fluorescent probes. The reason why this experiment uses these probes, was the assumption, that the positive charge occuring on the fluorescent probe will lead to the electrostatic interaction with the negatively charged polymer. As a result, the bond between acridine orange and polyelectrolyte was not clearly demonstrated, but the interaction with Rhodamine 6G have been proved.
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Diffusion characterization of hydrogels at microscopic level
Uher, Tadeáš ; Smilková, Marcela (referee) ; Sedláček, Petr (advisor)
This Bachelor’s thesis deals with study of diffusion in gels on microscopic level. The method of fluorescence correlation spectroscopy is used for the study of diffusion and this method is based on monitoring the diffusion coefficients in a confocal volume of studied substance. As fluorescence probe is used organic pigment called Rhodamin 6G and diffusion experiments are realized in hydrogel matrix, whose medium forms thermoreversible linear polycarbohydrate – agarose, with addition of reactive component – biopolymer called sodium polystyrenesulphate in certain concentrations. The purpose of the thesis is to research the impacts of interaction between diffusing pigment and specific type of hydrogel. The change of final diffusion coefficient is observed. It is assumed, that sodium polystyrenesulphate influences the diffusion of fluorophore (Rhodamin 6G) in agarose hydrogel.
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